commit: avoid race when creating orphan commits

diff --git a/replace_object.c b/replace_object.c
index cdcaf8cbe2f4e6c7a5b334fc2c43da6855df4654..0ab2dc137487259d50b69258e967792aa6c43619 100644 (file)
--- a/replace_object.c
+++ b/replace_object.c
@@ -3,8 +3,13 @@
 #include "refs.h"
 #include "commit.h"
 
+/*
+ * An array of replacements.  The array is kept sorted by the original
+ * sha1.
+ */
 static struct replace_object {
-       unsigned char sha1[2][20];
+       unsigned char original[20];
+       unsigned char replacement[20];
 } **replace_object;
 
 static int replace_object_alloc, replace_object_nr;
@@ -12,7 +17,7 @@ static int replace_object_alloc, replace_object_nr;
 static const unsigned char *replace_sha1_access(size_t index, void *table)
 {
        struct replace_object **replace = table;
-       return replace[index]->sha1[0];
+       return replace[index]->original;
 }
 
 static int replace_object_pos(const unsigned char *sha1)
@@ -24,7 +29,7 @@ static int replace_object_pos(const unsigned char *sha1)
 static int register_replace_object(struct replace_object *replace,
                                   int ignore_dups)
 {
-       int pos = replace_object_pos(replace->sha1[0]);
+       int pos = replace_object_pos(replace->original);
 
        if (0 <= pos) {
                if (ignore_dups)
@@ -36,12 +41,8 @@ static int register_replace_object(struct replace_object *replace,
                return 1;
        }
        pos = -pos - 1;
-       if (replace_object_alloc <= ++replace_object_nr) {
-               replace_object_alloc = alloc_nr(replace_object_alloc);
-               replace_object = xrealloc(replace_object,
-                                         sizeof(*replace_object) *
-                                         replace_object_alloc);
-       }
+       ALLOC_GROW(replace_object, replace_object_nr + 1, replace_object_alloc);
+       replace_object_nr++;
        if (pos < replace_object_nr)
                memmove(replace_object + pos + 1,
                        replace_object + pos,
@@ -60,14 +61,14 @@ static int register_replace_ref(const char *refname,
        const char *hash = slash ? slash + 1 : refname;
        struct replace_object *repl_obj = xmalloc(sizeof(*repl_obj));
 
-       if (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->sha1[0])) {
+       if (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->original)) {
                free(repl_obj);
                warning("bad replace ref name: %s", refname);
                return 0;
        }
 
        /* Copy sha1 from the read ref */
-       hashcpy(repl_obj->sha1[1], sha1);
+       hashcpy(repl_obj->replacement, sha1);
 
        /* Register new object */
        if (register_replace_object(repl_obj, 1))
@@ -86,12 +87,19 @@ static void prepare_replace_object(void)
        for_each_replace_ref(register_replace_ref, NULL);
        replace_object_prepared = 1;
        if (!replace_object_nr)
-               read_replace_refs = 0;
+               check_replace_refs = 0;
 }
 
 /* We allow "recursive" replacement. Only within reason, though */
 #define MAXREPLACEDEPTH 5
 
+/*
+ * If a replacement for object sha1 has been set up, return the
+ * replacement object's name (replaced recursively, if necessary).
+ * The return value is either sha1 or a pointer to a
+ * permanently-allocated value.  This function always respects replace
+ * references, regardless of the value of check_replace_refs.
+ */
 const unsigned char *do_lookup_replace_object(const unsigned char *sha1)
 {
        int pos, depth = MAXREPLACEDEPTH;
@@ -107,7 +115,7 @@ const unsigned char *do_lookup_replace_object(const unsigned char *sha1)
 
                pos = replace_object_pos(cur);
                if (0 <= pos)
-                       cur = replace_object[pos]->sha1[1];
+                       cur = replace_object[pos]->replacement;
        } while (0 <= pos);
 
        return cur;